#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int n, m, dp[55][55][55][55];
vector<vector<int> > vect;
int cut(int l, int r, int u, int d){
if (l==r&&u==d)return 0;
if (dp[l][r][u][d]!=-1)return dp[l][r][u][d];
int res=LLONG_MAX/2;
for (int i=l; i<r; ++i)res=min(res, cut(l, i, u, d)+cut(i+1, r, u, d));
for (int i=u; i<d; ++i)res=min(res, cut(l, r, u, i)+cut(l, r, i+1, d));
return dp[l][r][u][d]=res+vect[d][r]-vect[d][l-1]-vect[u-1][r]+vect[u-1][l-1];
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>m;
memset(dp, -1, sizeof(dp));
vect.resize(n+1, vector<int>(m+1, 0));
for (int i=1; i<=n; ++i)for (int j=1; j<=m; ++j)cin>>vect[i][j], vect[i][j]+=vect[i][j-1]+vect[i-1][j]-vect[i-1][j-1];
cout<<cut(1, m, 1, n);
}
